Back to the Trevithick Dredger Engine
by John
The 6″ vertical boiler is virtually completed. Well, actually, I still have to make a Duplex steam pump, fit a steam injector, make a steam delivery manifold, paint some bits…. but yeah, emotionally, for me it is finished. I will get back to those bits as the mood takes me.
So I have picked up the bits of the Trevithick steam dredger engine. I will concentrate on the boiler, so I can get the AMBSC certification, then take a leisurely approach to the engine. You know, 2 weeks to the boiler certification then another 4 weeks to finish the engine. Or something like that.
As you can see, I have redesigned the inspection hatch, and made the new version. This is still not quite authentic, but it is much closer to the London Science Museum example. The inspection hatch will be permanently closed, silver soldered shut. And the wording reflects the fact that this is a model. The model hatch is circular, whereas the LSE example is something between a circle and an ellipse. Trouble is that we do not know what is original Trevithick and what was altered in 1870. So I do not feel too guilty that I am guessing.
Sorry about the poor focus. I will retake this shot later. You can read my new AMBSC ID number. I do feel presumptuous writing my name the same size as Trevithick.
I have marked the boiler perforations and will drill the holes then make the bronze bushes.
A hi res photo of the dredger engine in the LSM. You can see that the inspection hatch is something between a circle and an ellipse, not a rectangle. And that firedoor hinge is definitely sus.
johnsmachines 
l;ooks great John,
Why first making the bronze bosses? If theperforations are a little to wide you have to make new ones. Firts make the holes and you can mayby safe some bronz.
Regards Huib
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Hi Huib, yes, holes first then bushes. John
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Ah, yes, mistake in caption corrected.
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I think the reason there are no holes on the inspection cover may be because in the photograph it appears to be standing off of the face of the boiler a few inches bolted to a metal ring spacer. I assume that the ring had been cut off from the boiler in the picture in question, hence no rivet holes. Only a guess.
Very nice work you are doing and at 1/8 scale quite a project, I hope to see it completed.
Jenny from Bridlington
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Hi Jenny, that makes sense. However it would mean that the Rees cyclopaedia drawing is not quite accurate, because I cannot see a spacer in that drawing. Which is not unlikely. Completion date unpredictable, but should not be more than a month or two when I have finally decided on the design. John
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